Tout has many different adverbial uses. This paper deals with one of them, which is hardly ever taken into account, or even mentioned, in grammar books: tout can be used as a premodifier of the subordinator comme in comparative constructions. Comme is the only qu-word that can be premodified by tout. However, there are heavy constraints on the premodification of comme by tout and the presence of tout, very often, prevents the actualization of meanings (time or cause for instance) which would be possible otherwise. The paper aims to show that, in comparative constructions, it is sometimes compulsory, sometimes optional or sometimes impossible to insert tout. These variations are a consequence of the basic meaning of tout, which is defined, after Franckel 1989, as a sign marking the absence of any form of otherness. The article ends with a few remarks on tout comme (with no constituent after comme).